JAKARTA, Indonesia — The Chinese military has become significantly more aggressive and dangerous over the past five years, the top U.S. military officer said during a trip to the Indo-Pacific that included a stop Sunday in Indonesia.

General Mark Milley, chairman of the Joint Chiefs of Staff, said the number of intercepts by Chinese aircraft and ships in the Pacific region with American and other partner forces has increased significantly over that time, and the number of unsafe interactions has risen by similar proportions.

“The message is the Chinese military, in the air and at sea, have become significantly more and noticeably more aggressive in this particular region,” said General Milley, who recently asked his staff to compile details about interactions between China and the United States and others in the region.

His comments came as America redoubles its efforts to strengthen its relationships with Pacific nations as a counterbalance to China, which is trying to expand its presence and influence in the region. The Biden administration considers China its “pacing threat” and America’s primary long-term security challenge.

General Milley’s trip to the region is sharply focused on the China threat. He will attend a meeting of Indo-Pacific chiefs of defense this coming week in Australia, where key topics will be China’s escalating military growth and the need to maintain a free, open and peaceful Pacific.

American military officials have also raised alarms about the possibility that China could invade Taiwan, the democratic, self-ruled island that Beijing views as a breakaway province. China has stepped up its military provocations against Taiwan as it looks to intimidate it into unifying with the communist mainland.

American military officials have said Beijing wants to be ready to make a move on the island by 2027. The United States remains Taiwan’s chief ally and supplier of defense weapons. U.S. law requires the government to treat all threats to the island as matters of “grave concern,” but remains ambiguous on whether the U.S. military would defend Taiwan if it were attacked by China.

China’s top military officer, General Li Zuocheng told General Milley in a July 7 call that Beijing had “no room for compromise” on issues such as Taiwan. He said he told General Milley that the United States must “cease U.S.-Taiwan military collusion and avoid impacting China-U.S. ties and stability in the Taiwan Strait.”

The United States and others are also worried that a recent security agreement that Beijing signed in April with the Solomon Islands could lead to the establishment of a Chinese naval base in the South Pacific. The United States and Australia have told the Solomon Islands that hosting a Chinese military base would not be tolerated.

“This is an area in which China is trying to do outreach for their own purposes. And again, this is concerning because China is not doing it just for benign reasons,” General Milley told reporters traveling with him. “They’re trying to expand their influence throughout the region. And that has potential consequences that are not necessarily favorable to our allies and partners in the region.”

General Milley’s visit to Indonesia is the first by a joint chiefs chairman since Admiral Mike Mullen in 2008. American leaders have crisscrossed the Asia-Pacific in recent months, including high-profile visits by Secretary of Defense Austin and Secretary of State Blinken.

The Biden administration has been taking steps to expand its military and security relationship with Indo-Pacific nations as part of a campaign to build a stronger network of alliances in China’s backyard and counter China’s growing influence.

General Milley declined to provide specific numbers of unsafe Chinese interactions with American and allied aircraft and ships. But Mr. Austin, in a speech in Singapore last month, referred to an “alarming increase” in the number of unsafe intercepts by People’s Liberation Army aircraft and vessels.

Mr. Austin specifically pointed to a February incident where a PLA navy ship directed a laser at an Australian P-8 maritime patrol aircraft, but there have been a number of others.

A surveillance aircraft controlled by Canada was recently intercepted by a Chinese fighter in international airspace. Also, American ships are routinely dogged by Chinese aircraft and vessels during transits, particularly around man made islands claimed by Beijing in the South China Sea.

General Milley said there have been Chinese intercepts with Japan, Canada, Australia, Philippines and Vietnam. They all, he said, have seen a “statistically significant” increase in intercepts, and the number of unsafe incidents has increased by an “equal proportion.”

General Milley, who met on Sunday with the chief of the Indonesian National Defense Forces, General Andika Perkasa, said Pacific nations like Indonesia want the American military involved and engaged in the region.

“We want to work with them to develop interoperability and modernize our militaries collectively,” General Milley said, in order to ensure they can “meet whatever challenge that China poses.”

He said Indonesia is strategically critical to the region, and has long been a key partner with the United States.

General Milley, who spent the afternoon at General Andika’s military headquarters, was greeted with a massive billboard bearing his photo and name, a military parade and a large television screen that showed a video of his career.

At the end of the visit, General Andika told reporters that Indonesia has found China to be more assertive and “a little bit aggressive” with naval vessels in connection with territorial disputes with his country.

Earlier this year, the United States approved a $13.9 billion sale of advanced fighter jets to Indonesia. And in Jakarta last December, Secretary Blinken signed agreements for enhanced joint naval exercises between the United States and Indonesia.

China has condemned American efforts to expand its outreach in the region, accusing the United States of trying to build an “Asian NATO.” During a speech in Singapore, Austin rejected that claim. “We do not seek a new Cold War, an Asian NATO or a region split into hostile blocs,” he said.